Michael Garibaldi explains to Mary Ann Cramer, an ISN reporter recently arrived on the station, that Cmdr. Sinclair is out in a Starfury. Cramer is annoyed that the commander has been avoiding her since she was sent to cover the two year anniversary of Babylon 5 going on line.

In Med Lab, Dr. Stephen Franklin is surprised when he is visited by an old professor of his, Vance Hendricks. Dr. Hendricks offers Franklin a great adventure like nothing he has ever had. Meanwhile, in the docking bays, Nelson Drake confronts a worker who suspects Drake is trying to smuggle something on board. When the worker persists, Drake kills him.

Cmdr. Sinclair and Garibaldi learn about the death of the crewman, who at first glance seems to have died from a heart attack (although Garibaldi is immediately skeptical). Dr. Franklin orders an autopsy.

Back in Med Lab, Hendricks introduces Drake as his partner, and shows him artifacts they retrieved from a long dead planet, Ikarra VII. He explains that the dig was sponsored by Interplanetary Expeditions and retrieved the artifacts from a sealed vault a mile beneath the surface. Despite their age, the artifacts are in mint condition. Hendricks explains that the artifacts are organic in nature, and hopes they will provide the breakthrough to organic technology – but he needs Dr. Franklin's help. Franklin agrees to help. While the two doctors go to confer elsewhere, Nelson begins unpacking the rest of the items. When he touches one of the artifacts, streams of energy lash out at him, knocking him against the far wall.

Cmdr. Sinclair checks into C'n'C. Garibaldi reports everything is quiet and they have to wait another day to learn about the autopsy. Lt. Cmdr. Ivanova explains to Sinclair that they have been detecting some strange energy fluctuations the past few hours. Sinclair also admits he is not looking forward to the interview he has scheduled the following day with Ms. Cramer.

While they work long into the night, Dr. Franklin confronts Hendricks as being more of a scavenger than creator, admitting that he thinks corporations sponsoring digs is too much like grave digging. Hendricks responds that corporations have the funding where universities do not, and that he has seen great wonders throughout his searches.

Garibaldi, meanwhile, is meeting again with Mary Ann Cramer. Once she asks him to comment on being fired from his last five jobs, however, he quickly takes off.

In MedLab that night, Nelson partially transformed, clasps one of the artifacts to his chest and it bonds to him. Dr. Franklin wanders back to MedLab, finding the place completely dark. Nelson emerges from the shadows, even more transformed. He mutters, "protect" and fires an energy pulse from his left arm, knocking Franklin unconscious.

The next day, Garibaldi and Sinclair go to see Franklin, with Garibaldi explaining how they found him. Franklin is woozy, but otherwise not seriously injured. Franklin explains the weapon he was attacked with was part of the organic devices they were researching, prompting Garibaldi to wonder if they truly were checked through customs.

Sinclair and Garibaldi then confront Hendricks about the attack. Vance denies knowing anything about why it attacked Franklin, and insists Nelson had been the one to take care of bringing them aboard. He explains he was able to learn that the devices graft themselves onto host bodies in order to carry out their programming. He offers to help stop the possessed Drake by learning more information from the artifacts.

In Downbelow, Nelson's transformation continues. He kills two Lurkers while shouting "protect." His weapon discharge is detected in C'n'C – and it's getting more powerful.

Garibaldi links Sinclair about the attack, explaining he is putting a team together to track down the possessed Drake. Cramer walks into C'n'C asking about the rumors of an attack. Sinclair orders to leave, but she persists in staying, making Ivanova "convince" her to leave.

Garibaldi's team finds Drake, now almost totally transformed into an Ikarran warrior. They confront him in Grey Sector, but their weapons are unable to harm it. After firing upon them, it withdraws by burning his way through the walls. The security team advances with C'n'C tries to monitor.

In Medlab, Franklin and Hendricks unearth a storage device among the artifacts. Franklin also notices a curious device from Nelson's bag, which he pockets without Hendricks seeing.

Garibaldi heads to C'n'C to check in. The command staff realizes that every time the weapon fires, he needs time to recharge – but that the periods of recharge are becoming much smaller while the energy level keeps growing. Fearing the weapon will head to the Central Corridor, where there are the most people, Garibaldi clears it out of civilians while calling in more security officers.

Franklin heads up to C'n'C as Sinclair gears up to join the security teams. They've located the weapon and it is heading straight for them. Franklin explains he's learn the history of the Ikarrans. Over the centuries, their world was invaded half a dozen times, with each invasion being more bloody than the last. The Ikarrans eventually developed organic weapons. However, the weapons were designed to not respond to anyone who was not a "pure Ikarran." Those who defined that term were religious fanatics and military extremists, who based the term on ideology rather than science. In the next invasion, 11 of the 12 weapons were deployed. They stopped the invaders – and they wiped out all other life on Ikarra VII, finding no one "pure." Sinclair asks if there is anything sentient inside the weapon to reason with, and Franklin says there is but that the logic of the weapon's program is suppressing it.

Sinclair joins the security team, brandishing a PPG rifle. They blast the Weapon with everything they have, but it shrugs off their fire and burns through to the level below. Sinclair decides the only way to stop it is to blow out part of the hull, blowing the weapon out into space. He tells Garibaldi to stand by while he lures it to one of the docking bays. When Garibaldi asks how he plans to do that, he responds by saying he's going to "make it mad."

Sinclair speaks to the weapon, appealing to the personality that was grafted into the weapon's programming. He mocks it, telling him he is a failure and that Ikarra VII is a dead world. He fires upon the weapon and it returns fire, pursuing him through the corridors and through customs, finally reaching a docking bay. The weapon keeps shouting it must protect Ikarra, and Sinclair keeps responding that it failed its mission. Cornered in the docking bay, Sinclair orders the area sealed and prepared to be depressurized – even if it means his own death. Sinclair keeps speaking to the Weapon, telling it to access the memories of Nelson, who has seen Ikarra VII. The weapon does so--and sees its world is nothing left but a desert, dead for 1000 years. In rage and grief, the device separates itself from Nelson and deactivates.

Later, Franklin confronts Hendricks. He explains how he found the device, a tool used for cardiac stimulation that can induce heart attacks. Realizing the device had been used to murder the customs guard, Franklin spoke to Nelson (now recovering) who confirmed Hendricks knew the devices had not been properly brought onto the station. Vance explains that IPX is a front for a bio-weapon developer. He held back on delivering the artifacts until he could better learn how they worked, hoping to net a huge amount of money from doing so. Hendricks protests that he had no idea Nelson would murder the customs agent, and no idea anyone would be hurt. He then offers to split the money with Franklin if he just agrees not to turn him in. Franklin says it is too late – he calls in two security guards who take Vance away.

While Sinclair enjoys a drink in his own quarters, he receives a visit from Garibaldi. The whole station is talking about how Sinclair risked his life to stop the weapon. Michael criticizes Sinclair for putting his life in danger recklessly, saying he knows many people from the Earth-Minbari War have a "need to be the hero," to desire going out in a blaze of glory. Sinclair realizes he has no answer for his old friend, but promises to work on it.

In the Zocalo, Ivanova meets Franklin, who is thinking a lot about the Ikarrans and wondering if something like what happened to them could happen on Earth. Ivanova is unusually optimistic such a thing could never happen – until two security officers approach Franklin with orders from Earthforce Bio-weapons division to confiscate the artifacts.

In his office, Sinclair finally has his interview with Mary Ann Cramer, who asks him if space "is worth it?" Sinclair responds emphatically yes – that because the sun will eventually go out, unless mankind goes to the stars, everything they have achieved was for nothing.

"The last time I gave an interview, they told me to relax and tell them what I really felt. Ten minutes after the broadcast I got transferred to an outpost so far off the star maps you couldn't find it with a hunting dog and a Ouija board."

– Sinclair

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"What's the worse that could happen? They fire you, ship you off to the Rim, and I get promoted to commander. I don't see a problem here."

– Garibaldi, to Sinclair about his interview with the ISN reporter

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"Don't! You're too young to experience that much pain."

– Ivanova to the ISN reporter, blocking her way to Sinclair in C'n'C

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"You forgot the first rule of the fanatic: when you become obsessed with the enemy, you become the enemy!"

– Sinclair

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"If you need something, I'll be over there getting drunk with the other aliens."

– Ivanova, to Franklin

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"No. We have to stay here and there's a simple reason why. Ask ten different scientists about the environment, population control, genetics and you'll get ten different answers, but there's one thing every scientist on the planet agrees on. Whether it happens in a hundred years or a thousand years or a million years, eventually our Sun will grow cold and go out. When that happens, it won't just take us. It'll take Marilyn Monroe and Lao-Tzu and Einstein and Morobuto and Buddy Holly and Aristophenes .. and all of this .. all of this was for nothing unless we go to the stars."